Pump device



Dec. 6, 1966 H. E. ADAMS 3,289,918

PUMP DEVICE Filed May 20, 1964 9 Sheets-Sheet 1 lA/VW/U? #44 410 6 ADA/w Q4612 9 ATTOFNF/f H- E. ADAMS Dec. 6, 1966 PUMP DEVICE 9 Sheets-Sheet -3 Filed May 20, 1964 INVENTOR. 6442a!) flD/4ms Dec. 6, 1966 H- E. ADAMS 3,289,913

PUMP DEVICE Filed May 20, 1964 9 Sheets-Sheet 5 INVENTOR. HARM 0 6,4 04% 9am Mia/Q H-E-ADAMS PUMP DEVICE Dec. 6, 1966 9 Sheets-Sheet 4 Filed May 20, 1964 V M RQQK F" g @Q m Tv [NI/[A702 #42040 514mm" 02m A; sm-

H. E. ADAMS Dec. 6, 1966 PUMP DEVICE 9 Sheets-Sheet 5 Filed May 20, 1964 IFI 924/22 4" wa A 7' 7019/1/06 Dec. 6, 1966 H. E. ADAMS 3,289,918

PUMP DEVICE Filed May 20, 1964 9 Sheets-Sheet 6 I, TV 2: Y T '7 M fi l/( 02D 22 4 BY w /66 920% 57 92M? ATTOR NE )5 H. E. ADAMS PUMP DEVICE Dec. 6, 1966 9 Sheets-Sheet '7 Filed May 20, 1964 INVENTOR. HA ROAD 15 4mm H. E. ADAMS PUMP DEVICE Dec. 6, 1966 9 Sheets-Sheet 8 Filed May 20, 1964 IIILNITll IN V E NTOR. H4204!) Ap4/m H. E. ADAMS Dec. 6, 1966 PUMP DEVI GE 9 Sheet$Sheet 9 Filed May 20, 1964 INVENTOR 624 040 634.0401) \N% NQ fiwm ATTO R N EYS United States l atent O 3,289,918 PUMP DEVICE Harold E. Adams, South Norwalk, Comm, assignor to The Nash Engineering Company, Norwalk, Conn., a corporation of Connecticut Filed May 20, 1964, Ser. No. 368,967 20 Claims. (Cl. 230-79) This invention relates to improved liquid ring compressor systems in general and in particular to an improved method of and system for supplying seal liquid to a liquid ring compressor which extends the practical compression ratio range, increases the compressor life, reduces the chance of early compressor failure, raises the overall compressor efiiciency, and which is self regulating to automatically supply the correct amount of seal liquid for each operating pressure irrespective of changes in the internal operating clearances of the compressor. The present invention also relates to an improved liquid ring compressor unloading and stopping system which assures a smooth and orderly transition of the compressor from a pumping state to a non-pumping state and which unloads the compressor with a minimum waste of compressed gases.

The present invention furthermore provides protection against continual stalling of the liquid ring resulting from overload conditions or reduced operating speed, or momentary stopping such as might be caused by loss of or reduced voltage or other power supply defiiciency.

In compressors (or pumps) of this type, water or other seal liquid is revolved in a circular or elliptical path within a lobed casing by a rotor containing a plurality of shrouded blades which form radially extending, open ended, displacement chambers. The liquid, which only partially fills the interior of the casing, follows the interior wall of the casing due to centrifugal force and while passing along a lobe of the casing alternately recedes from, and is forced back into, the displacement chambers within the rotor. Stationary inlet and outlet ports cooperate with the inner open ends of the rotor displacement chambers to permit the air or other gas to be drawn into and discharged from the chambers after compression. This general type of pump is well known in' the art and is fully described, for instance, in applicants prior United States Patent No. 2,195,375 dated March 26, 1940.

The present standard liquid ring compressors commercially available have generally been limited to a maximum of 85 p.s.i. delivery pressure. While it has always been possible through the careful control of the manufacturing tolerances of the compressor parts and the use of laboratory and selective assembly procedures to construct a compressor capable of delivering higher than 85 p.s.i. pressures, this limit has been generally accepted as the safe limit for reasonable compressor life consistent with cost considerations. In practice, when a compressor constructed to standard manufacturing tolerances operates at 100 p.s.i. or higher over a long time, it deteriorates and soon fails to give the desired service at 100 p.s.i. discharge pressure. This trouble is due to an accumulation of several marginal factors. An important factor is the matter of clearances within the compressor. Wear increases these clearances and leads to the final breakdown of performance. This is not so critical if the liquid ring compressors are restricted to services not requiring over 85 p.s.i. gauge discharge pressure.

A principal point of wear involving seal liquid leakage occurs at the sealing surfaces around the outer diameter of the rotor end shrouds which help confine the liquid ring to provide the desired displacement. Obviously, the pumps performance will gradually degrade as these operating clearances increase due to the fact that more seal 8,289,918 Patented Dec. 6, 1966 ice liquid will escape through these enlarged clearances and: therefore subtract front the total aiiiount of seal liquid that enters each of the displacement chambers on the corripressing cycle. The other important sealing surfaces are at the inner diameter of the rotor where it revolves adjacent the stationary central inlet and discharge poi't member.

The seal liquid in my earlier US. Patent No. 2,195,375 was directed to the clearances between the rotorand the casing at points adjacent to the periphery of the rotor and to the running clearance between the rotor and the central port member.

In general, the seal liquid directed to these important sealing areas was fed to the compressor from either an outside source of seal liquid such as a fresh water supply main or was obtained by cooling and recirculating the seal liquid discharged by the pump into the separator on the pressure side.

All liquid ring compressors for proper operation continuously require replenishment of the seal liquid therein for three basic purposes, namely; sealing of clearances, cooling, and expulsion or purging.

In sealing arrangements of prior art liquid ring compressors, most of the liquid used for sealing and all other purposes had to be discharged through the compressed air central discharge port of the compressor. The discharge ports were sized and timed to handle the combined discharge of compressed air and the seal liquid for the three basic sealing requirements outlined above. On low compression ratios or where a relatively small amount of work was being done by the compressor, these liquid quantities were small and there was no problem in ejecting the liquid through the comparatively large low compression ratio discharge ports.

As the field of the liquid ring compressor was extended to higher compression ratios and/ or higher pressures, this increased the requirement for all three types of seal liquid service. The increased work of compression required more liquid to cool and remove the greater amount of heat generated in the higher compression process. The higher pressure differences generated within the compressor required increased amounts of sealing liquid to seal the running clearances of the compressor and the higher compression ratio required additional expulsion liquid to adequately purge the final discharge of gas.

All of these added requirements for more and more seal liquid mposed a disproportionate burden on the compressor to discharge this required extra amount of seal liquid. The discharge port, however, could not be enlarged to take the increased amount of liquid as any increase in its arc length would reduce the compression ratio. On the contrary, the discharge port had to open later in the compression cycle and extend through a smaller circular arc to permit the compression within the rotor displacement chambers to attain the higher compression ratio before the port opened. This gave a reduced area and time for the expulsion of the increased quantity of seal liquid required for the higher compression ratio pumps.

In addition -to the handicap of the smaller exhaust port required for the higher compression ratio, there is the added handicap that, in order to operate over the higher compression ratio and at higher discharge pressures, the compressor speed had to be increased to provide the necessary increased kinetic energy. This additional speed of rotation at the same time further reduced the time duration of each port opening. I

As a result of these cumulative effects, the liquid ring compressor reaches a work limit where it is impossible to get rid of the required amount of seal liquid along with the compressed gas through the limited size of the exhaust port. When this point is reached the normal kinetic action-of the compressor breaks down and the liquid ring stalls, or queers, as it is sometimes called. With the occurrence of a stalled ring, the compressor rotor then merely violently churns the liquid within the casing in an unorganized manner. This phenomenon in liquid ring compressors is characterized by a loud noise and severe cavitation. At the same time, of course, the compressive action ceases or is greatly reduced.

It allowed to run against a dead end or high pressure in this stalled manner, the compressor does not resume normal functioning. The running in a stalled condition, i urtherm'ore, has the further effect that the cavitation of the rotor blades and easing releases particles of metal which accelerate the erosion of the compressor parts, in particular those areas of the sealing surfaces where the tolerances are most critical.

When the sealing surfaces are worn so that the clearance is increased from operation of the compressor in the stalled condition or from other causes of wear between the surfaces, a still greater flow of seal liquid is induced and required to seal these enlamged clearances. This additional sealing liquid is discharged with the other liquid through the discharge ports of the compressor. Such addition to the already loaded water handling requirement of the compressor is eventually enough, as wear clearances progress, to throw the compressor into a stalled condition at progressively lower and lower discharge pressure limits.

Thus with the state of the art and the design of present compressors, there is a practical operating pressure limit of approximately 85 p.s.i. gauge.

The present invention comprises a method and apparatus which avoids the limitations of the prior art systerns as above outlined by obviating the need for discharging the liquid required -for sealing purposes through the pump discharge ports. The system of the invention recirculates the liquid used for sealing purposes between the liquid ring and the sealing surfaces. Thus about /3 of the total liquid load that must be passed through the pump [for the aforementioned three purposes is diverted from passage through the discharge ports.

In the present invention means are provided to draw off sealing liquid at an intermediate point on the periphery of the pumping lobe. The sealing liquid thus obtained is directed through a short conduit under its intermediate lobe pressure directly back to reseal the critical operating clearances of the pump. The seal liquid is effectively fed back or recirculated within the compressor itself at the desired pressure level for the aforementioned rotor sealing duty without further regulation or adjustment and without having to pass through the dischange port. The recirculated seal liquid does not have to be brought up to the full pressure difierence established by the compressor and forced through the final discharge ports of the compressor as in the prior art liquid ring pumping systems. Thus, the unnecessary work of pressunizing the sealing liquid to discharge it against the full compressor discharge pressure is avoided.- In prior art sealing systems the high discharge pressure 01f the spent seal liquid must be reduced through an orifice to a lower intenmediate pressure as required for sealing purposes. Such pressure reduction is avoided in applicants novel system. 'A further and most important aspect of the invention is, however, that the quantity of sealing liquid is selfadapting to compensate for wear in the pump parts and does not have to be squeezed through the limited discharge port of the compressor at full pres sure and thus precipitate early stall.

Another feature of this apparatus and method of sealing is the built-in automatic or self-adapting compensation of the sealing liquid flow rate with changing clearances between the operating parts of the pump. As the critical rotor sealing clearances increase with time and wear, the recirculated seal liquid automatically increases to constantly seal these enlarged spaces. The intermediate lobe pressure is maintained on the compensating seal system up to the sealing surface clearances these being the only restrictions to the recirculated flow. The relationship is a direct one with the flow rate varying with the clearance growth.

This increased sealing liquid flow resulting from the enlarged operating clearances does not, unlike prior art seal liquid supply systems, impose an extra added burden on the discharge port Of the compressor to pass more and more volume of seal liquid. 'The invention thereby reduces the chance for early failure or the compressor and extends its life considerably. It also reduces the power required and, therefore, increases the overall compressor efliciency.

A further feature of applicants novel seal liquid supply system is provision of means for an automatic supply of purging liquid under conditions when this extra liquid is required. This liquid is supplied from the liquid discharged by the compressor into its associated separator through a separate liquid line connected to the compensating seal liquid supply system, through a check valve and flow limiting orifice.

During low pressure operation where no purging liquid is required or desired there is no flow through this fluid circuit because the intermediate lobe pressure applied to the compensating seal conduit system is higher than the separator discharge pressure. The check valve, therefore, is held closed and prevents back flow and loss of seal liquid from the compensating system into the separator. As the discharge pressure of the pump increases, there is a corresponding increased requirement for purging service and the system Will automaticallysupply such need because the pressure in the separator then exceeds the intermediate lobe pressure of the compensated seal liquid system and the check valve will open and cause a flow of purging liquid through the metering orifice to the compensated seal system. Therefore, concurrently with the requirement for additional seal liquid for purge purposes at higher pressures, the pressure in the separator at this time is higher than the pressure in the compensating seal system and, therefore, additional liquid from the separator is supplied for purge purposes.

The higher the discharge pressure and the greater the requirement for purging service, the more liquid is supplied. The water for purge services so added is discharged with the compressed air through the discharge port. The liquid for cooling purposes is added to the compressor near the inlet portion of the port cylinder at a pressure lower than the liquid required for sealing purposes. This cooling liquid also serves to seal the clearance spaced adjacent the central inlet port cone of the compressor. The liquid added for cooling purposes at this point is expelled along with the purging liquid through the discharge port. The quantity of liquid required for cooling purposes ideally varies With the amount of compression work being accomplished by the compressor. It is not practical normally to vary this supply of cooling liquid with compression ratio. Rather it is the practice to provide for a predetermined fixed supply of cooling liquid, sufficient for the normal high pressure or high compression ratio operation of the compressor. This supply of liquid is, of course, more than necessary when the compressor is operating at low pressure, as during idle or starting-up operation. During low pressure operation, "as at start-up on a high compression ratio characteristic compressor, the resulting larger volume of low pressure air must be discharged through the small discharge ports designed for the higher compression ratio service. The discharge of the excess cooling water, in this case, together with the large low pressure air volume, results in' choking at the small discharge ports with resulting build-up in internal compressor pressure and power input to expel this mixture. This undesirable condition is automatically offset in applicants method of bypassing .1) the excess cooling liquid through the compensating seal system directly to the separator through a restricting orifice and check valve by taking advantage of the fact that during this cycle of low pressure operation, the pressure in the lobe connection to the compensating seal system is higher than the discharge separator pressure.

A further feature of applicants novel seal liquid supply system is provision of means for an automatic bypassing around the compressor of excess cooling liquid when the compressor is caused to operate at low pressure differentials. This feature further reduces the possibilities of choking at the discharge port and obviates the requirement for excess power to discharge the unnecessary cooling liquid with the large volume of low pressure air through the small discharge ports during the low pressure operation.

Accordingly, a principal object of the invention is to provide a novel method and apparatus for supplying seal liquid to a liquid ring compressor which extends its compression ratio range, increases its life, and improves its efliciency.

Another object of the invention is to provide a novel self-adaptive seal liquid supply system which compensates for changing internal clearances in the pump and automatically supplies sufficient sealing liquid as required.

Another object of the invention is to provide automatic supply means for adding additional liquid for purging purposes under conditions when an extra amount of purging liquid is required and to cease addition of such extra purging liquid when no requirement therefor exists.

Another object of the invention is to provide a seal liquid supply system that is self-regulating to the extent that it does not require the re-adjustment of the primary inlet seal fluid flow rate during temporary operation at low compression ratios or at compression ratios for which the primary seal liquid flow rate was not selected.

Another object of the invention is to provide a seal liquid supply system for a high compression ratio pump which when operated at low compression ratios requires a reduced amount of horsepower and operates smoothly throughout a wide compression range.

The present invention also relates to an improved method and apparatus for unloading a liquid ring compressor system. The term unloading as used herein refers to the process whereby the compressor action of the pump is destroyed when a pressure control switch or the like senses the desired upper limit of pressure on the discharge side of the pump. In order to prevent the upper pressure limit from being exceeded, it is conventional to continue to operate the liquid ring pump but to merely make it ineffective by venting or unloading the seal liquid from the lobe periphery. The prior art unloading procedure is undesirable for two reasons. First, in liquid ring pumps having a pair of opposed lobed pumping portions, it has been the usual procedure to unload only one lobe to destroy the pumping eifect of the liquid ring. This unsymmetrical unloading of the ring creates a radical imbalance of forces upon the rotor. The aforedescribed compensating and self-adaptive seal liquid supply system, by its very nature, provides means to vent each of the lobes of the pump simultaneously and thereby unloading when accomplished with the compensating seal system means of the invention is symmetrical and balanced.

The second and most undesirable aspect of present Ullloading systems is that when the compression capability of the liquid ring pump is destroyed by the venting of the seal liquid, the high pressure stored air on the discharge side of the compressor takes charge and instantly reverses and expands back through the pump with equal or greater force than normally exerted by the rotor. This expanding force drives the broken up liquid ring back through the rotor and chamber and suddenly acts as a brake or momentary reverse turbine drive. The expanding air and the broken up liquid ring are driven against the rotation 6 of the blades to escape, partly through the inlet and finally out through the one open unloader opening in one of the two lobes of a conventional two lobe pump, or through the one unloader opening of a conventional single eccentric lobe pump.

On high pressure compression this reverse expansion back through the just unloaded liquid ring compressor becomes a destructive force. A measure of this sudden expansion efi ect is dramatically observed in stopping of a compressor. The above described prior art unloading technique is in efiiect an expansion brake which stops a 3500 rpm. rotor in three or four revolutions with a loud characteristic shriek. The present invention overcomes the unbalanced forces associated with unloading or stopping of a liquid ring compressor and at the same time lets the compressor rotor come to an easy coasting stop with little or no associated noise.

The arrangement of the present invention accomplishes these improved results by first equalizing the air pressure across the compressor to eliminate the objectional and potential reverse expansion of the discharge pressure back through the compressor against the broken up seal liquid. Once the inlet and outlet pressures of the pump have been equalized, the liquid of the liquid ring is discharged through the unloader port under its own difierential centrifugal pressure. This gives a smooth, orderly unloading which is quiet and does not stress the pump components. While the above description of the unloading phenomenon has been described in association with the renden'ng of the liquid ring pump inoperative while it continues to be motored it should be appreciated that the same unloading concept is equally applicable to the stopping where the drive motor is cut off. A further feature of this apparatus and method of control is the provision :ior protection of the compressor against damage due to voltage failure or reduction of speed of the driving motor or to overload from operation at over pressure or from any other overloading cause, such as, excess liquid supply. In a high pressure compressor, it is a characteristic that at the several points in the lobe sweep, the static pressure generated under normal operation is lower than the rated discharge pressure of the compressor. The velocity pressure of the liquid ring does not register as gauge pressure at this point. When, however, the normal velocity of the ring is upset for any reason and it stalls or queers, as previously pointed out, the static pressure of the discharge is immediately transmitted back to the liquid ring and by sensing this increase or surge in static pressure in the ring by a pressure control switch, this switch can immediately operate the aforedescribed unloader system to unload the compressor and protect it from damage. This increase in ring pressure occurs whenever its velocity is reduced such as would be the case when the speed of the driver is reduced or stopped, as in a momentary voltage failure or stopping of the compressor or from the inadvertent reduction in drive speed of a turbine driver, etc. Any reduction in velocity with accompanying increase in ring pressure serves as a control signal to operate the unloading system and thus protect the compressor from cavitation damage.

Accordingly, another principal object of the invention is to provide a novel method and means for unloading a liquid ring compressor system so that an orderly transition between an operative and non-operative condition is effected.

Another object of the invention is to provide a novel unloading system for a liquid ring compressor which equalizes the pressure between the compressor intake and outlet at the time that the pumping action of the liquid ring is destroyed.

Another object of the invention is to provide an unloading system which supplies intake vapor to the inlet of the pump at the normal discharge pressure of the pump.

Another object of the invention is to provide a novel unloading system which vents the pump discharge to atmosphere (or to essentially the intake pressure of the pump) to thereby equalize the inlet and discharge pressures thereof during unloading. Another object of the invention is to provide a novel protection against stalling conditions caused by voltage failure or from reducedspeed operation of the driver.

Still another object of the invention is to provide a novel protection against stalling conditions caused by overload on the compressor from excess liquid, excessive pressure or other overload causes.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this specification. For a better understanding of the invention, its operating advantages and the specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which:

FIG. 1 is a longitudinal sectional elevation of a liquid ring compressor according to the invention, FIG. 1 being taken substantially along the line 1-1 of FIG. 3 with parts in elevation and ports broken away;

FIG. 2 is a transverse sectional elevation of the liquid ring compressor of the invention showing schematically an arrangement of conduits connected with the compressor;

FIG. 3 is an end view of the compressor as seen from the left side thereof'in FIG. 1, with the motor of FIG. 1 omitted;

FIG. 4 is a longitudinal sectional elevation showing another embodiment of a liquid ring compressor according to the invention;

FIG. 5 is a fragmentary transverse sectional view taken along the line 55 of FIG. 4 in the direction of the arrows;

FIG. 6 is a longitudinal sectional elevation of a third embodiment of a liquid ring compressor according to the invention;

FIG. 7 is a fragmentary transverse sectional elevation taken along the line 7-7 of FIG. 6 in the direction of the arrows;

FIG. 8A fragmentarily illustrates a different arrangement of a bleeding chamber communicating With one of the lobes;

FIG. 8B shows the arrangement of the bleeding chamber of the other lobe of the same compressor as FIG. 8A;

FIG. 9A shows still another arrangement of a bleeding chamber communicating with one of the lobes;

FIG. 9B shows the arrangement of the bleeding chamber communicating with the other lobe of the compressor of FIG. 9A;

FIG. 10 shows the construction of a metering orifice which provides a restricted controlled flow of liquid through a conduit;

FIG. 11 is a longitudinal sectional illustration of a nonreturn valve structure which permits fluid t-o flow in both directions;

FIG. 12 is a schematic illustration of a fluid-compressing system according to the invention;

FIG. 13 shows a different construction of the cooling liquid supply of FIG. 12;

FIG. 14 shows a diiferent construction of the excess cooling liquid discharge and purging liquid recirculating portion of FIG. 12.;

FIG. 15 shows a fluid-compressing system of the invention particularly designed for providing automatic unloading of the compressor;

FIG. 16 shows a diiferent construction of a valve for placing the separator and inlet of the system of FIG. 15 in communication with each other;

FIG. 17 schematically illustrates the connection between pressure sensing devices and solenoid valves of the system of FIG. 15;

FIG. 18 shows the unloading arrangement of the in vention also applied to a conventional system;

FIG. 19 shows an unloading arrangement of the invention also applied to a conventional system;

FIG. 20 shows a mechanical unloading system which operates in a manner analogous to the electrical system of FIG. 19; and

FIG. 21 is a sectional elevation of the pressure responsive valve of FIG. 20.

Liquid ring compressor Referring first to FIGS. 1-3, the liquid ring compressor 24 is mounted on a suitable base 26 which also carries a driving motor 28 which rotates the compressor 24. The compressor includes a rotor 30 which has a pair of shrouds 32 and 34 respectively located in parallel planes which are perpendicular to the axis of the rotor 39, and the rotor 36 also includes a plurality of substantially radial blades 36 which extend between and are fixed at their opposite ends to the shrouds 32 and 34 so as to define therewith the displacement chambers 38, shown most clearly in FIG. 2. These displacement chambers 38 are open to their outer ends 40 and at their inner ends 42.

The compressor 24 also includes a housing 44 which includes a cup-shaped casing member 46 surrounding the rotor and a head member 48 which has a central portion 50 extending intoand surrounded by the rotor 30. The casing members 48 and 46 will be understood to be fluidtightly fixed to each other by suitable bolts and gaskets, sealing members, and the like (not shown). As may be seen from FIG. 2, the central portion 50 of the casing member 48 has an inner tubular portion 52 and an outer tubular portion 54 interconnected by radial webs 56 which I are distributed about the axis of the compressor so as to define a pair of opposed inlet chambers 58 and a second pair of opposed discharge chambers 60. The outer tubular portion 54 of the central portion 50 of the casing is formed wtih a pair of opposed inlet openings 62 through which fluid passes into the rotor chambers 38 and a pair of outlet openings 64 communicating with the discharge chambers 60 and through which the compressed fluid passes into the discharge chambers 60.

As is also shown in FIG. 2, the casing 44 does not extend along a circle. It is provided with upper and lower portions, as viewed in FIG. 2, which are spaced from the periphery of the rotor 30 so as to define therewith a pair of opposed lobes 66. The rotor 30 rotates in a clockwise direction, as viewed in FIG. 2, and during normal operation a liquid ring extends along the outer periphery of the rotor 30 into the lobes 66, and this ring turns with the rotor. During the clockwise rotation of the rotor 30, as viewed in FIG. 2, this liquid ring will, at the ends 68 of the lobes 66, recede away from the axis of the rotor so as to suck fluid in through the openings 62 from the inlet chambers 58 and displace the fluid, which is to be compressed, radially away from the axis of the rotor in the chambers 38. As the liquid ring recedes away from the rotor axis the fluid to be compressed is sucked into the chambers 38 until the liquid ring reaches the portions of the lobes 66 shown in FIG. 2 directly above and below the rotor where the lobes have their greatest width, and from the latter region up to the ends 70 of the lobes 66 the liquid ring returns back toward the axis of the rotor so as to compress the fluid in the displacement chambers 38, and it is this compressed fluid which discharges through the openings 64 into the discharge chambers 60.

The fluid, generally a gas or a gas and vapor, which is to be compressed is supplied to the compressor 24 through an inlet conduit 72 having a suitable non-return valve 74, and this inlet conduit 72 communicates with spaces in the casing member 48 which communicate with the inlet chambers 58. The motor 28 is connected through a suitable coupling 76 witha drive shaft 78 which is rotated by the motor 28 and which is connected to the hub 80 of the rotor 38, this hub being formed by an inner portion of the shroud 34, and the hub 80 is suitably keyed at 81 9 to the shaft 78 so as to rotate therewith. The casing members 48 and 46 are respectively provided with suitable sealing glands 82 and 84 through which the drive shaft 78 passes. In addition, the casing carries brackets 86 which support bearings 88 which in turn support the shaft 78 for rotary movement.

Spaces in the interior of the casing member 46 communicate with a discharge conduit 90 which directs the compressed fluid from the chambers 60 to a suitable separator means (referred to below) in which the compressed fluid is separated into gas and liquid.

Cooling and sealing liquid is supplied to the compressor 24 from any suitable source through a conduit 92 (FIG. 1), and this cooling liquid is received in the space 94 between the shaft 78 and the central portion of the casing member 48, so that the cooling liquid flows along the shaft 78 at its portion which is surrounded by the central casing portion 50, and the central casing portion 50 is formed with a pair of ports 96 communicating with the inlet chambers 58 so that the seal liquid flows through the ports 96 into the chambers 58 with the gas from the inlet conduit 72 into the displacement chambers 38 and through the compressor out through the discharge conduit 9% in the manner described above. The afore described pump operation and structure will be readily recognized by those skilled in the art to be characteristic of liquid ring pumps.

Self-cmpensating liquid seal As is shown most clearly in FIG. 1, the outer periphery of the shroud 32 is surrounded by and located closely adjacent to an inwardly directed circular surface of the casing member 46 to form the interface 98, and the inner periphery of the shroud 32 forms the interface 190 with an outwardly directed frustoconical surface of the outer wall of the central member 511 of the casing member 48. The shroud 34 forms at its outer periphery an interface 182 with an inwardly directed surface of the casing member 46, and the inner periphery of the shroud 34 forms with a second outwardly directed frustoconical surface portion of the outer wall of the central portion 50 of the casing member 48 the interface 104. It is essential to provide proper seals at these interfaces, and there is a limit to the manufacturing tolerances and precision of assembly which can economically be provided to maintain the stationary and rotary compressor parts tight at these interfaces while at the same time guaranteeing free rotary movement of the rotor 3G with respect to the casing 44 of the compressor 24.

The present invention solves the problem of sealing these interfaces in the following manner:

Insofar as the interface 1114 is concerned, the cooling and make-up liquid entering through the conduit 92 into the chamber 94 will be received at the interface 1% so as to form a liquid seal at the interface 104, so that there is no particular problem with respect to the sealing of the interface 104. This cooling and make-up seal liquid, in addition to cooling the shaft 78 and forming make-up liquid, as well as maintaining a seal at the interface 104, serves to cool and lubricate the sealing glands 82 and 84.

With respect to the remaining interfaces 98, 100, and 102, the casing 44 is provided with a pair of bleed chambers 1% located at the widest parts of the lobes 66 and communicating with these lobes through the slots 103, respectively, as is shown in FIG. 2 as well as in FIG. 1. A conduit system 110 communicates with the pair of iced chambers 106 to receive liquid therefrom, and because =the liquid in the lobes 66 is at the pressure derived from the centrifugal fonce of the rotor 30, there will be a substantial pressure in the liquid in the bleed chambers 106 and thus in the conduit means 110 communicating therewith. At the casing cover 48 the conduit means 110 includes a pair of conduit portions 112 communicating through casing passages 113, respectively, with a shroud sealing chamber 114 defined between the shroud 32 of the rotor 30 and the casing 44, and this shroud sealing chamber 114 communicates on the one hand with the interface 98 and on the other hand with the interface 100. In addition the conduit means includes a pair of conduit portions 116 communicating with a second shroud sealing chamber 118 defined between the shroud 34 and the casing member 46 and communicating with the interface 102.

Thus, the self-compensating liquid seal of the invention functions to draw sealing liquid at intermediate portions of the lobes into the bleed chambers 106, and at the intermediate lobe pressure this sealing liquid is directed into the shroud sealing chambers 114 and 118 so as to provide sealing liquid substantially at the intermediate pressure of the lobes. This sealing liquid which is thus continuously supplied to the critical interfaces is obtained internally from within the compressor and is recirculated from the lobes to the shroud sealing chambers and from the latter back to the lobes without in any way interfering with the normal operation of discharge ports 64. The conduit means 110 also communicates with a conduit 120 providing a common connection for the entire compensating system to a separator means, referred to below, and liquid for purging service is supplied through this connection 120. Also, excess cooling liquid is bypassed through the connection 120 to the separator means, as described below.

By avoiding the need for passing the spent sealing liquid through the normal discharge ports of the compressor, there is more room for passage of the compressed gases therethrough. In addition, as the clearances at the interfaces increase due to wear and maladjustment, larger seal liquid flow rates are required in order to provide proper sealing. However, because of the recirculating nature of the sealing system of the invention and the unlimited supply at the intermediate pressure of the lobes to the interfaces, the necessary sealing liquid flow rate is automatically obtained in a self-adjusting and selfad-aptive manner. In prior systems, as these clearances increased, adequate sealing of the enlarged clearances could only be obtained by making a manual readjustment of the liquid flow to meet the new seal requirements. Also, in prior systems, the increased requirements for seal flow had to be discharged through the discharge ports 64, 64, and this requirement imposed added restriction to the passage of compressed gases therethrough. Of course, increased work was also required to discharge the increased liquid quantity, and eventually the increased liquid required to be passed through the discharge ports of prior art pumps, with increasing clearances, eventually resulted in the stalling of the liquid ring at progressively lower and lower discharge pressures.

The make-up liquid supplied through the conduit 92 may be obtained from a city fresh water or other supply system or it may be recirculated from a separator or receiver assembly described below. For the purposes of understanding this aspect of the invention, the source of the cooling liquid supplied to the conduit 92 is unimportant.

According to the embodiment of the invention illustrated in FIGS. 4 and 5, the compressor 24a has its casing 44a provided with members 46a and 48a, and in this embodiment there are also a pair of bleed chambers 106a communicating through slots 108a with the lobes 660:. However, with this embodiment there is no external conduit means camparable to the conduit system 110 of FIG. 1. Instead the end shroud sealing chambers 114a and 113a communicate directly with the bleed chambers 106a through a conduit means 110a formed by simple openings passing through the ends of the bleed chambers directly into the shroud sealing chambers, and in this way the sealing liquid at the intermediate lobe pressure passes directly through the openings 110a in to the shroud sealing chambers so as to seal the interfaces 98, 100, and

102, and thus the path through which the sealing liquid circulates is considerably shorter than in the embodiment of FIGS. l-3. The common connection 120a for the compensating sealing system to the separator means cornmunicates in this case directly with the lower bleed chamber 106a. Except for these differences the embodiment of FIGS. 4 and 5 is the same as that of FIGS. 13.

The embodiment of the invention which vis illustrated in FIGS. 6 and 7 is particularly simple since bleed chambers as such are not even required. With this embodiment the compressor 24b also has the casing 44b provided with the member 46b, and this member 46b is formed at its peripheral portions which directly surround the peripheries of the rotor shrouds with diammetrically opposed pairs of notches 110b, so that in this embodiment there is in fact an interruption in the interfaces between the outer peripheries of the rotor shrouds and the casing and at these interruptions there or provided the upper and lower pair of notches 11011 for each rotor shroud. These notches 11% form the conduit means of the em- 'bodiment of FIGS. 6 and 7, and the notches communiicate directly with the shroud sealing chambers 11% and 11%. Thus, with the embodiment at the central portions of the lobes 66b the liquid at the intermediate pressure within the lobes communicates directly through the notches 11% with the shrouds sealing chambers, and in this way the construction is considerably simplified and the circulating path for the sealing liquid is even shorter than in the case of FIGS. 4 and 5.

The embodiment of FIGS. 6 and 7 is provided with a lower chamber 122 communicating through a slot 124 with the lower lobe at its central portion, but this lower chamber 122 is simply a means for providing communication between the self-compensating sealing system and the common circuit 12% which connects the liquid sealing system with the separator means.

In actual practice the the constructions of FIGS. 4 and 6 are preferred to that of FIG. 1, because of the greater simplicity and increased efficiency, but for the purpose of clarity of understanding the invention reference is made below to the compensating sealing system of FIG. 1.

It is .not essential to locate the bleed chambers or the notches 11% of FIG. 6 precisely at the centers of the lobes 66. Thus, referring to FIGS. 8A and 8B, it will be seen that the bleed chambers 126a and 12615 of these figures respectively correspond in all respects to the bleed chambers 106, respectively, of FIG. 2, the only difference being that these bleed chambers of FIGS. 8A and 8B are displaced beyond the central portions of the lobes closer to the discharge ends 70 thereof than the inlet ends 68. These bleed chambers 126a and 126k communicate through slots 128a and 128b respectively, with the lobes at portions thereof which are at pressures higher-than the pressures at the precise centers of the lobes, with the result that with a construction as shown in FIGS. 8A and 8B it is possible to provide a compensating sealing system at a pressure higher than is possible with the embodiment of FIG. 2.

On the other hand, in the case of FIGS. 9A and 9B, the bleed chambers 130a and 130k communicate through slots 132a and 132b, respectively, with the lobes 66, and these bleed chambers are displaced with respect to those of FIG. 2, with which they are otherwise identical, nearer to the inlet ends 68 of the lobes than the discharge ends 70 thereof, so that the arrangement of FIGS. 9A and 9B will provide a compensating sealing pressure less than that of FIG. 2. The bleed chambers of FIGS. 8A and 8B communicate through a conduit means 110c with the shroud sealing chambers and with the connection to the separator means, so that the conduit means 1100 is identical with the conduit means 110 described above, and in the same way the conduit means 110d of FIGS. 9A and 9B communicates with the shroud sealing chambers and with a common connection to the separator means, so that except for the displacement of the bleed chambers 12 indicated in FIGS. 8A-9B the structures are identical with that of FIGS. 1-3.

Thus, while the position of the bleed chambers will be in general the position shown in FIGS. 8A and 8B, it is possible to provide other positions for compressors designed for particular purposes. With an arrangement as shown in FIGS. 8A and 8B, for typical pound discharge pressure compressor, the pressure maintained in the compensating sealing system varies from about 40 lbs. to 60 lbs. as the compressor discharge goes from 20 lbs. to 100 lbs., respectively.

Excess cooling liquid removal and purging liquid supply Referring now to FIG. 12, there is illustrated therein a compressor 126 having the above-described construction of FIGS. 1-3. It is supplied through a conduit 128 with a fluid which is to be compressed, and the compressed fluid is discharged through a discharge conduit 130 to a separator means 136. Cooling and make-up seal liquid is supplied to the compressor 126 through the conduit 132 which has a valve 148 which is manually opened before the operations are started. Downstream of the valve 148 is located a non-return valve and a solenoid valve 152 which is normally closed but is maintained open through the electrical circuit of the system during normal operation. Downstream of the solenoid valve 152 is an orifice assembly 153 which regulates the rate of flow of cooling and make-up liquid through the conduit 132 into the compressor.

The compensating sealing system of the compressor 126 includes a conduit means 134 identical with the conduit means 110 and communicating in the same way with bleed chambers which in turn communicate with the lobes, as described above in connection with FIGS 1-3.

In the separator means 136 the high pressure which is discharged from the compressor is separated into a gas which accumulates at the upper part of the separator means 136 and a liquid which accumulates at the lower part thereof, and a floating ball-valve assembly 138 opens automatically to discharge liquid from the separator means 136 through a conduit 140 leading to a suitable drain, for example, when the liquid in the separator means 136 reaches a predetermined elevation. During normal operations there will be discharged from the separator means 136 through the conduit 140 precisely the same amount of liquid as is supplied to the compressor through the conduit 132. The compressed gas is discharged from the upper part of the separator means 136 through a conduit 142 which has a non-return valve 144 preventing the compressed fluid from backing up into the separator means, and from this conduit 142 the compressed gas is taken to any desired location. 7

The arrangement of FIG. 12 includes a conduit 146 connected to the compensating sealing system conduit means 134 and corresponding to the common connection 120 referred to above for connecting the compensating sealing system to the separator means 136.

As may be seen from FIG. 12, the conduit 146 communicates with a pair of branches 154 and which are in parallel with each other and which together communicate through a common conduit 147 with the interior of the separator means 136 at its lower portion where the liquid accumulates. The upper branch 154, as shown in FIG. 12, includes a metering orifice assembly 158 and a non-return valve 156 which permits the liquid to flow only in a direction from the conduit 146 to the separator means 136. On the other hand, the parallel branch 160 includes a non-return valve 162 and a metering orifice assembly 164, and the valve 162 permits the liquid to flow only in a reverse direction from the separator means 136 back to the conduit means 134 through the common connection 146 thereof. In addition the conduit 146 communicates throughpart of the branch 160 with a manually operable valve 166 and a drain conduit 168 which is used only to drain out the entire 13 system when it-isto be put out of operation, so that except on rare occasions the valve 166 will be closed and does not enter into normal operation.

The metering orifice assemblies 153, 158, and 164 each may have a construction as shown in FIG. 10. Thus, referring to FIG. it will be seen that the metering orifice assembly 170 includes a simple fitting 172 adapted to be connected into the conduit where the orifice assembly is to be situated, and the fitting 172 carries a transverse plate 174 formed with an orifice 176, and it is the size of the orifice 176 which determines the rate of flow of liquid through the particular conduit which has the assembly 170 located therein.

During normal operation of the system of FIG. 12 when the compressor is supplying compressed air and vapor to the separator means 136, the solenoid valve 152 is held open so as to permit a continuous flow of liquid through the conduit 132 into the compressor for cooling purposes. The amount of cooling liquid supplied is metered by the orifice assembly 153 so as to be just sufficient cooling liquid for high pressure operation of the compressor. During normal operation at the designed high pressure capability of the compressor, the pressure existing in the separator means 136 will exceed the pressure in the compensating sealing system. Accordingly, the pressure diiferential between the separator means 136 and the compensating sealing conduit means 134 will be effective to automatically supply an extra amount of liquid from the separator means through conduit 160 and orifice 164 to the compensating sealing system and from the latter to the compressor for purge purposes. Purging liquid is a requirement associated with higher compression ratios to expel or discharge the compressed charge of gas out through the discharge ports. The discharge of the smaller volume of higher density gas requires a greater amount of liquid to insure complete purging or sweeping out of the compressed gas at the final stroke. With a typical 100 lb. compressor design, the compensating seal system pressure is approximately 50 lbs. when the discharge pressure in the separator is at 50 lbs., but as the separator pressure is increased to 100 lbs. the compensating sealing pressure only rises to 60 lbs., thus providing a 40 lb. differential to deliver purge liquid. At this time the non-return valve 156 will prevent liquid from flowing from the separator means 136 through the branch 154 to the compensating sealing system conduit means 134, but the non-return valve 162 will permit such a flow to take place through the metering orifice assembly 164, and the greater pressure of the liquid in the separator means 136 will be effective to open the non-return valve 162. Thus, there will be an automatic return of liquid from the separator means to the compensating sealing system for purging purposes during normal high pressure operation when the pressure in the separator means 136 is considerably above the pressure of the compensating sealing system. The metering orifice assembly 164 controls the rate of flow of purging liquidback to the compressor at this time.

During operation of the system at low pressures when no extra purge liquid is required or wanted, there will be no flow through the check valve 162 inasmuch as the intermediate lobe pressure that exists under these conditions will be higher than the discharge pressure and thus higher than the pressure of the liquid in the separator means so that the valve 162 will be closed at this time. In this way, when the compensating seal system pressure is higher than the separator pressure the closing of the check valve 162 prevents backflow and loss of sealing liquid from the compensating sealing system. However, if the compressor is operated at still lower discharge pressures, the amount of cooling liquid required for the lower pressure compression is substantially less than that supplied by the orifice assembly 153 which is designed to supply the larger amount of cooling liquid required at the normal high pressure operation of the compressor. The compressor, however,

will often be required, with a given system, to operate at lower pressures, and in such event the larger amount of cooling liquid is unnecessary and detrimental because it is difficult to discharge all of this liquid through the relatively small discharge ports of the compressor along with the increased volume of gas and vapor that exists at these lower discharge pressures. For a given compressor, the volume of gas at 20 lbs. discharge pressure would be more than three times the gas discharge volume when operating at lbs. gauge. Under such low pressure operating conditions, a false or unusable back pressure is built up within the compressor rotor buckets, which requires additional power and at times even results in the stalling or queering of the liquid ring, which would further cause additional high power consumption, cavitation, and even breakdown of compressor performance. As has been explained above in the introduction, by avoiding the need for pumping this unnecessary amount of cooling liquid out through the normally small discharge ports of the compressor during low pressure operation there is more room for the passage of greater volume of gas of low pressure which is discharged at this time.

Referring to FIG. 12, it will be seen that the orifice assembly 158 and the non-return valve 156 of the branch 164 come into play at this time to provide a path of flow for the excess cooling liquid from the compensating sealing system directly through the conduit 147 into the sep arator means 136 which at this time is at a lesser pressure than the compensating sealing system, so that in this way there is no requirement for the excess cooling liquid to flow through the dis-charge ports of the compressor. Thus, it will be seen that while the check valve 156 prevents flow to the compensated seal system from the separator 136 when the compressor is operating at high pressures, at low pressure operation the pressure existing in the compensating seal system is greater and at such times this superior pressure opens the check valve 156 to discharge the excess amount of cooling liquid (limited by the control orifice assembly 158) directly from the bleed chambers to the separator 136, thus avoiding the necessity of discharging the excess cooling liquid through-the limited area of the compressor discharge ports with the unfavorable results described above.

With a typical 100 lb. compressor design, the compensating seal pressure does not go below 40 lbs., even when the compression discharge is only 10 to 20 lbs. In this way there is provided a differential pressure of roughly 30 ibs. for bypassing the excess cooling liquid throughthe conduit 154 to the separator in the manner described above.

FIG. 14 fragmentarily illustrates another structure for supplying purge liquid from the separator means to the compressor and for eliminating excess cooling liquid directly to the separator means instead of through the discharge ports of the compressor. In the embodiment of FIG. 14 the common connection 146 for the conduit means 134 of the compensating sealing system is connected through a single conduit 178 to the separator means 136.

This conduit 17 8 is provided with a non-return valve 180 and an orifice assembly 182, which may have the structure of FIG. 10 with a suitably sized orifice.

The details of the valve 180 are shown in FIG. 11. As may be seen in FIG. 11 the valve 180 includes a valve housing 184 having in its interior the apertured transverse wall 186 through which the liquid flows, and a clapper 188 closes the valve to prevent fluid from flowing from the compensating sealing system to the separator means as in a conventional check valve structure. However, in this case the clapper 188 is formed with an orifice 190. During normal high pressure operation, when the separator is at a higher pressure than the compensating sealing system, the clapper 188 will be raised by the liquid flowing from the separator to the compressor so that the orifice 190 will have no part in the operations and the purging liquid will be automatically supplied from the separator back to the compressor in the manner described :above. However, at low pressure operation the excess 'cooling liquid which reaches the valve 180 will be able to flow through the orifice 190 into the separator 136, so that in this way the valve assembly 180 is also capable of :accommodating flow of excess cooling liquid through the conduit 178 to the separator 136, thus avoiding the necessity of discharging this excess cooling liquid through the discharge ports of the compressor.

An alternative system for supplying cooling liquid to the compressor is shown in FIG. 13. As may be seen from FIG. 13 a conduit 192 communicates with the liquid in the lower portion of the separator 136, and through a valve 194 the conduit 192 communicates with a heat exchanger 198 which through a conduit 199 and a suitable orific'e assembly 200 (in accordance with FIG. communicates with a valve 202 which is opened when this cooling system is used. The cooled recirculated seal liq- '=uid passes through conduit 132' which is connected in the same way as the conduit 132 of FIG. 12 to the compressor. Cooling liquid for the heat exchanger 198 is supplied through a separate conduit 204 and a valve 206 which is opened when the heat exchanger is used, and the cooling liquid of the heat exchanger is discharged through a discharge conduit 208 and an open valve 210, which may be closed for the purpose of shutting off the cooling system when the apparatus is not being used. Thus, with this alternate system of FIG. 13 cooling and make-up liquid may be derived directly from the separator means itself for the purpose of supplying cooling and sealing liquid to the compressor 126, and with this arrangement either the supply conduit 132 from a city water system may not be used or it may be used simply for the purpose of initially filling this system after which the city supply is shut off and the entire system of the invention is self-sustaining.

It is to be noted that with the system of FIG. 13 very little liquid will be discharged through the drain 140 since the liquid normally discharged through the drain 140 will instead be recirculated through the cooling system of FIG. 13 and the floating valve assembly 138 will seldom reach a height suflicient to open the discharge 140.

Automatic unloading system Referring now to FIG. 15, it will be seen that there is shown therein a system substantially identical with that of FIG. 12. The same parts are designated by the same reference characters, and it will thus be seen that the compressor 126 is supplied with fluid through the inlet 128 controlled by a check valve 224 for preventing the compressed fluid from returning to the lower pressure of the inlet service. The compressed fluid is discharged through the conduit 130 to the separator means 136. The selfcornpensating sealing system described above is also incorporated, and the conduit means 134 thereof communicates through the connection 146 with the branches 154 and 160 which in the manner described above provide for automatic discharge of excess cooling liquid at low pressure and automatic return of purging liquid at high pressure. The cooling liquid is supplied through the conduit 132 which, when the apparatus is used, has its valve 148 opened, and a check valve 150 prevents return of cooling liquid away from the compressor while a solenoid valve 152 is maintained open during the normal operations, this valve 152 normally being closed when the system is not in use, as will'be apparent from the description below in connection with FIG. 17. The gas which is under pressure in the separator means 136 discharges through the conduit 142 and the check valve 144 to the location where it is desired to use the gas, and a manually operable valve 143 isvmaintained open and is only provided for the purpose of shutting ofl the apparatus when it is not in use.

The outstanding feature of the embodiment of FIG. 15 is that the discharge conduit 142 for the gas under pressure is connected directly to the inlet conduit 128 for the gas which is to be compressed through a conduit 212 which is connected to the conduit 128 downstream of the check valve 224 and to the conduit 142 upstream of the check valve 144, so that the gas discharging through the conduit 142 can communicate directly with the inlet 128 through the conduit 212. However, such communication is prevented during normal operation by a solenoid valve 214 which is normally open but which is maintained closed during operation of the system under normal conditions.

Also connected to the conduit 128, just downstream of the check valve 224, is a discharge conduit 216 having a metering orifice assembly 220 and a shut otf valve 218 which is opened when it is desired to provide relief to the outer atmosphere through the conduit 216, the rate of bleed to the atmosphere being controlled by the orifice assembly 220 upon opening of the valve 218. This valve 218 is closed when it is desired not to use the atmospheric relief or bleed line 216.

Downstream of the check valve 144 in the discharge conduit 142 for the gas under pressure is a conduit 226 which carries a pressure sensing means 222. This pressure sensing means operates a switch of the electrical circuit in a manner which is shown diagrammatically in FIG. 17.

Referring to FIG. 17 it will be seen that the conduit 226 includes a cylindrical portion in which a portion 228 is slidable, and a spring 230 urges the piston to move against the pressure of the fluid in the conduit 226. A threaded plug 232 engages the spring 230 for adjusting the compression thereof so that the piston 228 will move in opposition to the spring 230 when the pressure in the conduit 226, and thus in the conduit 142, builds up to a predetermined upper limit pressure. The pressure sensing means 222 is located in an electrical circuit 236 which is connected to the electrical supply lines in any suitable way, and a pair of contacts 238 are bridged by a con ductor 240 which is insulated from the piston rod 234 so that normally when the pressure in the discharge conduit 142 be below the predetermined upper limit for which the spring 230 is set the contacts 238 will be electrically connected to each other through the switch member 240 and thus the solenoid 244 of the valve 152 and the solenoid 248 of the valve 214 will be energized. The result is that the valve 152 which is normally closed by the spring 242, as shown diagrammatically in FIG. 17, is maintained open by the energized solenoid 244, and the valve 214 which is normally maintained open by the spring 246, as shown diagrammatically in FIG. 17, is now maintained closed by the energized solenoid 248.

However, it is clear that when the pressure in the discharge conduit 142 reaches the upper limit for which the pressure sensing means 222 has been set, as by adjustment of the plug 232, the switch 240 will be displaced away from the contact 238 thus opening the circuit 236 and deenergizing the solenoids 244 and 248 so that the spring 242 will now close the valve 152 and the spring 246 will open the valve 214.

The result of opening of the valve 214 when the upper pressure limit is reached is that the inlet 128 is im- .mediately placed at the same pressure as the outlet 142 and the inlet and dischargeconduits of the compressor 126 immediately have their pressures equalized. Thus,.the inlet and outlet pressure of the compressor will be essentially the same, except for minor pressure loss characteristics through the valve 214 and the connecting'piping 142, 212, 128. The check valve 224 prevents the escape of the equalizing gas to the atmosphere. Therefore when the valve 214 opens, .the inlet128 of the compressor is immediately pressurized and held to essentially the same pressure as the compressor discharge and the differential pressure workload is immediately reduced. to the point where the compressor is merely recirculating its displacement capacity of gas at the 'density of the discharge pressure. The compressor is creating very little pressure differential between its own inlet and discharge connections.

17 The compressor is still pumping, however, and recirculating full capacity of gas at the discharge density at this instant.

The liquid ring of the compressor at this time is developing a liquid pressure and reaction within the lobes due to normal centrifugal force. This internal liquid ring pressure is greater than the co-mpressors inlet pressure by this increment of centrifugal force, which in a typical 100 lb. design is about a 50 lb. differential.

Therefore, when the valve 214 opens and places the discharge pressure on the inlet of the compressor, the differential pressure created by the centrifugal action of the rotor places the lobes and the compensating sealing system pressure above the equalized inlet-discharge pressure. This higher differential liquid pressure, which will be a 50 lb. differential for a typical 100 lb. design as mentioned above, serves to immediately discharge liqiud from the lobes, through the compensating sealing conduit system 134 and through the branch 154 to the separator means 136 precisely in the same way that excess cooling liquid is discharged during low pressure operation, as described above in connection with FIG. 12. Therefore, under these circumstances the compressor, by centrifugal action only, discharges the liquid of its recirculating liquid ring to the separator 136, and it will thus very quickly purge itself of operating liquid and in this manner will quickly unload itself of further pumping ability because it has lost the motive liquid of its ring to produce a substantial pumping action. This unloading is accomplished smoothly and at no time does the discharge of the liquid ring suffer a disruptive back flow of gas or other disturbance, which now occurs under conventional systems of unloading. The liquid with the system of the invention is simply and quietly transferred to the separator by the centrifugal action of the rotor. In conventional systems of unloading, the liquid is discharged by the expansion and concurrent discharge of high pressure gas which carries the liquid with it to an atmospheric waste or drain connection.

Referring to FIG. 16, it will be seen that the valve 214 instead of being operated by a solenoid can be replaced by a valve 214' which is operated by a diaphragm in response to air pressure, and in this case the pressure sensing means 222 will instead, when it senses the upper limit of pressure, open the solenoid valve 250 placing a suitable source of air under pressure in communication with the diaphragm valve 214 for opening the latter and placing the pressure discharge 142 and suction inlet 128 directly in communication with each other through the conduit 212 with the results described above.

As is apparent from the above description and FIG. 17, the opening of the switch 24!) of the pressure sensing means 222 also deenergizes the solenoid 244 of the valve 152 so that the latter is automatically closed by its spring 242 and thus the supply of cooling liquid through the conduit 132 can no longer pass through the valve 152. However, there is provided, as shown in FIG. 15, a bypass conduit 252 bypassing the valve 152 and provided with a metering orifice assembly 254 having the construction of FIG. and provided with an orifice of a size suitable for maintaining a restricted supply of cooling liquid during the time when the valve 152 is closed, upon opening of the switch 240 of the pressure sensing means 222. The restricted flow provided through the bypass 252 at this time will furnish a small amount of liquid to the compressor serving to keep the interior surfaces of the compressor cool and lubricated under the light, unloaded conditions. There is insuflicient supply of liquid through the orifice assembly 254 during the unloaded operation to allow the compressor to form a normal liquid ring or to have any material performance ability. It is merely placed in this manner in a condition capable of running idly without heating up during extended periods of operation when the compressor is in its unloaded condition.

When the pressure in the discharge conduit 142 decays to a predetermined minimum pressure the switch 24% will again close so as to restore the electrical supply to the solenoid valves 152 and 214, thus opening the valve 152 and closing the valve 214, so that the liquid ring will again build up and the pressures will build up within the compressor and within the separator means 136, and the system will now continue to operate until the maximum pressure is again reached, whereupon the above unloading operations will again take place.

The unloading condition can be improved by using the bleed line 216. For this purpose the valve 218 is opened, and when the inlet conduit 128 is pressurized, as by opening of the valve 214 for unloading purposes, the metered flow through the orifice 220 to the outer atmosphere will slowly bleed down the compressor and separator system to atmospheric pressure. This operation will still further and more completely unload the compressor circuit by reduction in the density of the gas which is recirculated through the closed system. This basic unloading concept of the invention can be applied to many other types of operation.

Instead of using fresh make-up cooling water supplied through the conduit 132 in the manner shown in FIGS. 12 and 15, it is also possible to use the recirculated cooled circuit as indicated in FIG. 13. In this case the characteristics of the pressure drop through the conduits of the recirculating cooling system of FIG. 13 are adjusted by sizing or by orificing to produce just sufficient pressure differential, during the unloaded operation, between the separator 136 and the inlet 132 so that just sutficient cooling liquid will flow to the compressor to keep the compressor lubricated and cooled during unloaded operation.

If desired an alternate method of providing a circulating cooling liquid during unloaded operation is to place a small pump in the conduit 199 of FIG. 13 to operate only during the unloaded period so as to supply the necessary lubricating and cooling liquid.

If frequent unloading is required, and it is not desired to bleed the system down to atmospheric pressure at each unloading, the valve 218 may be maintained closed or the entire bleed line system 216 may be eliminated.

A particular feature of the invention resides in providing the unloading operations with the valves 152 and 214 in the positions which they normally assume when their solenoids are unenergized. As a result, if for any reason there is a voltage failure in the current which is supplied to the driving motor, the valves 152 and 214 will automatically close and open, respectively, so that the abovedescribed unloading operations will automatically take place. It is a fairly common occurrence in liquid ring compressors operating near their maximum pressure that if there is a fluctuation in the voltage of the driving motor or a momentary failure of voltage, there will be a dip in the compressor speed which will be sufficient to cause stalling of the liquid ring, and it is possible that if the compressor is allowed to operate after such a stalling occurrence it will continue to stay in the stalled condition without any recognition by the operator that such operation is taking place. Continued operation in the stalled condition produces extreme wear and tear on the compressor with subsequent cavitation damage thereto. It is therefore desirable to eliminate this not infrequent possibility of operation in a stalled condition, and provision of the above unloading system automatically prevents such stalling from taking place because any momentary voltage failure will automatically trigger the values 152 and 214 so that they will automatically close and open, respectively, with automatic unloading in the manner described above prior to stall occurrence.

It is possible for the liquid ring in a compressor or vacuum pump to become stalled for other reasons than power or voltage failure where the reduced voltage or power failure to the solenoid valve assemblies 152 and 214 serves automatically to unload the compressor and protest it from the stalled failure. For example, it may happen that the switch 240 will fail to function properly to unload the compressor at high pressure limit setting with the possibility that the compressor will try to build up pressures beyond its operating capacity. In such an event the ring would become stalled, but if the switch 240 failed to open, the compressor would continue to run in the stalled condition. Another condition of stalled operation might be encountered if the compress-or were driven by a steam turbine and the steam supply were reduced to the point where the turbine did not drive the compressor at a suflicient speed to maintain operation at the required discharge pressure. The liquid ring would in such a case also go into a stalled condition with resulting damage, and, in this case, there would be no voltage failure to take the compressor automatically into the unloaded condition as described above. Other conditions producing stall could be precipitated if too much liquid is supplied from the cooling water supply 132, or even if too little cooling liquid is supplied.

To take care of incipient stall conditions of this latter nature, an additional pressure sensing means 256 which may be identical with the pressure sensing means 222 is provided. This pressure sensing means 256 communicates through a conduit 258 with the conduit means 134 of the compensating liquid sealing system so that the pressure sensing means 256 senses the pressure of the liquid ring. Referring to FIG. 17, it will be seen that the pressure sensing means 256 includes the piston 260 slidable in a cylindrical extension of the conduit 258 and acting against the pressure therein with the aid of the spring 262 which is adjusted by the threaded plug member 264. The piston rod 266 carries and is insulated from a switch member 268 which normally bridges the pair of contacts 270 of the circuit 236 so that normally there will be no interruptions in the flow of current through the solenoids 214 and 248. However, when there is an unusually high pressure in the liquid ring of the compressor, the piston 260 will be moved by this pressure against the force of spring 262 to an extent suflicient to open the switch 268 and thus deenergize the solenoids 244 and 248 so that the valves 152 and 214 will operate in the manner described above to automatically unload the compressor.

For a given speed of operation, the pressure existing at the periphery of the liquid ring is fairly constant and does not vary to the same extent as the discharge pressure of the compressor. The liquid ring pressure is higher than the discharge pressure when operating at a relatively low pressure range, while on the other hand the liquid ring pressure does not equal the discharge pressure at higher discharge pressure operation, as was pointed out above. Thus, in a 100 lb. compressor design the liquid ring pressure may be only 50 or 60 lbs.

It may appear unusual that the lobe pressure, when operating at high discharge pressures, is less than the discharge pressure, but this fact follows from the condition that the pressure which is measured at the periphery of the lobe, for example at the bleeding chamber at the upper, part of the compressor, is only static pressure. The pressure of the equivalent velocity head of the circulating liquid ring is not included in this pressure measurement. The sum of the equivalent velocity head and the static pressure is greater than the resultant total pressure head measured by the pumps discharge. As long as the compressor is operating normally, therefore, at high pressure discharge, the measurement of static pressure at the lobe periphery by the pressure sensing means 256 remains fairly uniform and lower than the discharge pressure in the conduit 130. If, however, the liquid ring loses its velocity for any reason, and stalls the higher pressure existing in the discharge conduit 130 is immediately transmitted back through the liquid ring and is immediately sensed by the pressure sensing means 256. In other words, as soon as the kinetic velocity head of the moving liquid ring is destroyed, the pressure in the separator 136 and the discharge conduit 130 expands back through the discharge ports to place the entire casing, including its liquid ring, under the discharge pressure because the liquid ring has lost its energy by this stalling operationand permits such a reexpansion back through the discharge side. Such an operation, as previously noted, causes noise, cavitation, and damaging erosion to the compressor if allowed to continue running at any length of time under these conditions.

With the presence of the pressure sensing means 256 in a system as shown in FIG. 17, advantage is taken of the considerable increment of pressure differential between the normal static pressure of the liquid ring and the increase in pressure due to stalling as described above, and this increase in pressure operates the pressure sensing means 256 so as to open the circuit and thus deenergize the solenoids 244 and 248 with automatic unloading as described above. This breaking of the electrical supply serves to unload the compressor immediately and thus protects it from operation in a stalled condition. With the construction shown in FIG. 17 the pressure sensing means 256 will restart the compressor when the pressure again drops, but the arrangement can be such that the compressor will be maintained out of operation until the operator wishes to manually start the compressor again. Also, the pressure sensing means can be used to give an alarm, either audible or visible, so as to warn the operator of an abnormal condition which has produced a stalled operation.

The unloading system of the invention is applicable to conventional liquid ring compressors. In FIG. 18 such a conventional liquid ring compressor 126' is illustrated connected to the unloading system of the invention, and it will be noted that the compressor 126' is not provided with the self-compensating liquid sealing system of the invention. It is however connected with the unloading system of the invention, as illustrated in FIG. 18. In addition, there is a single bottom unloader connection 272 communicating with the lower lobe. In conventional unloading system, this bottom unloader connection would normally be connected to an atmospheric waste line and controlled by an unloading valve in the line to dump the liquid ring and expand the compressed air to waste when it was desired to unload the compressor. However, in adapting the unloader system of the invention to a known installation as shown in FIG. 18, the conduit 272 is connected to the bottom of the separator 136 and includes a metering orifice assembly 274 and check valve 276 which provide for unloading of the liquid ring when the valves 214 and 152 are operated for unloading purposes in the manner described above. The unloading features of FIG. 18 are identical with those described above and provide the advantages of the invention in that there will be protection against stalling and overloading without necessarily involving a compensating sealing system. Therefore, the advantages of the unloading system of the invention can be adapted to existing pumps and compressors by simple repiping as indicated in FIG. 18.

Of course, the arrangement of FIG. 18 will additionally provide for reduction in horsepower requirements for the compressor when it is operating at low pressures but supplied with a constant cooling liquid rate which has been set for a higher compression ratio. When operating at lower pressures, the lobe pressure is higher than the discharge pressure in the separator 136, as pointed out above, and under these conditions the excess cooling liquid will flow through the conduit 272, the orifice 274, and the valve 276 into the separator so that this arrangement does provide the added advantage of preventing discharge of the excess cooling liquid through the discharge ports of the compressor, so that the advantage of reducing horsepower requirements at low pressure operation Where there is a constant supply of cooling and make-up liquid is also achieved with the arrangement of FIG. 18.

FIG. 19 also shows how the structure of the invention for sensing the sudden increase in the pressure of the liquid ring during stalled operation can 'be used in a conventional system. Here again a conventional compres sor 126' is supplied through the inlet 128 with the gas which is to be compressed, and cooling liquid is supplied through the conduit 132 and in this case a simple manually operated valve 152' controls the conduit 132 which also may have a suitable metering orifice assembly. The compressed gas is discharged through the conduit 130 to the separator 136 where the gas under pressure is discharged through the conduit 142 which includes a pressure sensing means 222 which may be identical with the pressure sensing means 222 described above. Such a construction would normally include a conventional bottom unloader 280 having a valve 282 controlled by the pressure sensing means 222' so that when the latter sensed the maximum pressure for which the pressure sensing means is set the valve 282 is automatically opened so as to discharge the liquid ring through the conduit 280, the valve 282, and the drain line 284, and thus unload the system.

However, in accordance with the invention there is now provided in the conduit 280 an additional pressure sensing means 286 which will sense the sudden increase in the pressure of the liquid ring when for any reason there is a stalled operation resulting in loss of velocity head, so that the kinetic pressure is added to the static pressure as described above, with the result that the additional pressure sensing means 286 of the invention responds. This pressure sensing means 28-6 is operatively connected with the solenoid valve 282 in order to automatically open the latter in the same way as the pressure sensing means 222', so as to automatically unload the compressor and thus prevent the stalled operation with all of the advantages mentioned above.

FIGS. 20 and 21 show a system which is mechanically analogous to the electrical system of FIG. 19. This mechanical system may be used with a turbine or other mechanical drive, as well as with an electric motor drive. This system utilizes the high surge in pressure upon stalling to operate a conventional pop or safety valve 288, the details of which are shown in FIG. 21. Thus, the bottom unloader line 286 is connected with the safety valve 288 which when it opens will drain the liquid out through the line 290. As may be seen from FIG. 21, the conventional safety valve 288 includes a casing 292 in which is situated the valve 294 which will open in opposition to the spring 296 in a manner well known in the art, and a manually operable lever 298 is provided for manual operation of the valve whenever desired. Such a valve may set to pop :at or lbs. above the normal operating pressure of the liquid ring as sensed in the conduit 286. When stalling occurs the liquid ring pressure jumps to a higher value, approaching that of the discharge pressure, and this increasing pressure is sufiicient to actuate the safety valve 288 so as to unload the liquid ring to atmosphere through the conduit 290. The action of such safety valves is well known. They do not open until the pressure for which they are set is reached, and then upon opening, they open wide to fully relieve this system. After a considerable drop in pressure, when the system is relieved, the valve closes. Thus, a valve of this type will keep the compressor from operating continuously in a stalled condition.

While the invention has been disclosed above in connection with a two lobe liquid ring compressor, it is to be understood that the invention is equally applicable to single lobe pumps or compressor, or, for that matter, to pumps or compressors with more than two lobes. Furthermore, while electrically controlled valves have been described in the operation of the system, pneumatic or other types of control valves could be substituted without departing from the principles of the invention.

While various specific embodiments of the invention have been shown and described in detail to illustrate the application of the novel principles, it should be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In combination, a liquid ring compressor having a ring of liquid circulating therein and a recirculating seal liquid supply system, said compressor including; a casing, an annular rotor having a plurality of radially extending displacement chambers rotatably mounted within said casing to form at least one pumping lobe therebetween and a stationary central port member having inlet and discharge passageways cooperative with the inside diameter of said rotor, said recirculating seal liquid supply system comprising; a seal liquid bleed chamber in said casing in direct communication with each lobe and conduit means connecting each chamber with a radially inward portion of said casing adjacent the end of said rotor for recirculating seal liquid from the lobe to the area adjacent the rotor ends to seal the operating clearances between said rotor and said casing and between said rotor and said central port member, said conduit means having a terminal portion adapted to communicate said compressor with a pressure responsive means for supplying excessive cooling liquid to said compressor when said compressor operates above the normal operating discharge pressures thereof and for permitting egress of cooling liquid when said compressor is operating at pressures below said normal discharge pressures thereof.

'2. A liquid ring compressor unloading system comprising, in combination a liquid ring compressor means including a casing, an annular rotor having a plurality of radially extending open ended displacement chambers rotatably mounted within said casing to form at least one pumping l-o'be therebetween, and a stationary central port member having inlet and discharge passageways cooperative with the inside diameter of said rotor, a conduit for receiving the compressed gas discharge from said compressor means for substantially equalizing the pressure difference between said conduit and said inlet passageway, and means cooperative with said last mentioned means for withdrawing seal liquid directly from the interior of said casing to destroy the pumping effect of said compressor.

3. Apparatus according to claim 2 including in addition a recirculating seal liquid supply system, said sys tem comprising a seal liquid bleed chamber in said casing in direct communication with said lobe and conduit means connecting each chamber with a radially inward portion of said casing adjacent the end of said rotor for recirculating seal liquid from the lobe to the area adjacent the rotor ends to seal the operating clearances between said rot-or and said casing and between said rotor and said central port member.

4. In a liquid ring compressor, a rotor having a pair of annular end shrouds respectively located in parallel planes which are perpendicular to the axis of the rotor and a plurality of substantially radial blades extending between and fixed to said end shrouds and defining therewith a plurality of displacement chambers distributed about the axis of said rotor, a casing having a central portion surrounded by said rotor and including inlet and discharge chambers communicating with said displacement chambers of said rotor for respectively supplying fluid thereto and discharging fluid therefrom, said casing having an outer annular portion surrounding said rotor and defining therewith at least one lobe in which liquid first recedes away from the rotor axis at the region of one end of said lobe and then advances back toward said axis at the region of the other end of said lobe for sucking fluid into said displacement chambers through said inlet chamber of said casing and discharging compressed fluid back out through said displacement chambers and said discharge chamber of said casing, said casing defin- 

1. IN COMBINATION, A LIQUID RING COMPRESSOR HAVING A RING OF LIQUID CIRCULATING THEREIN AND A RECIRCULATING SEAL LIQUID SUPPLY SYSTEM, SAID COMPRESSOR INCLUDING; A CASING, AND ANNULAR ROTOR HAVING A PLURALITY OF RADIALLY EXTENDING DISPLACEMENT CHAMBERS ROTATABLY MOUNTED WITHIN SAID CASING TO FORM AT LEAST ONE PUMPING LOBE THEREBETWEEN AND A STATIONARY CENTRAL PORT MEMBER HAVING INLET AND DISCHARGE PASSAGEWAYS COOPERATIVE WITH THE INSIDE DIAMETER OF SAID ROTOR, SAID RECIRCULATING SEAL LIQUID SUPPLY SYSTEM COMPRISING; A SEAL LIQUID BLEED CHAMBER IN SAID CASING IN DIRECT COMMUNICATION WITH EACH LOBE AND CONDUIT MEANS CONNECTING EACH CHAMBER WITH A RADIALLY INWARD PORTION OF SAID CASING ADJACENT THE END OF SAID ROTOR FOR RECIRCULATING SEAL LIQUID FROM THE LOBE TO THE AREA ADJACENT THE ROTOR ENDS TO SEAL THE OPERATING CLEARANCES BETWEEN SAID ROTOR AND SAID CASING AND BETWEEN SAID ROTOR AND SAID CENTRAL PORT MEMBER, SAID CONDUIT MEANS HAVING A TERMINAL PORTION ADAPTED TO COMMUNICATE SAID COMPRESSOR WITH A PRESSURE RESPONSIVE MEANS FOR SUPPLYING EXCESSIVE COOLING LIQUID TO SAID COMPRESSOR WHEN SAID COMPRESSOR OPERATES ABOVE THE NORMAL OPERATING DISCHARGE PRESSURE THEREOF AND FOR PERMITTING EGRESS OF COOLING LIQUID WHEN SAID COMPRESSOR IS OPERATING AT PRESSURES BELOW SAID NORMAL DISCHARGE PRESSURES THEREOF. 